This project aims to understand how obesity causes its complications in non-adipose tissues. We will determine if long-standing diet-induced obesity (DIO) in normal rats leads to lipotoxicity of pancreatic islets of Langerhans and heart, thereby accounting for the diabetic and cardiac abnormalities that complicate the human counterpart of DIO. Normal Sprague Dawley rats fed a 60% fat diet become massively obese within 8 weeks. Within 6 months they develop hyperglycemia, suggestive of onset of islet dysfunction. Thus, the specific aims of this proposal are: 1) To determine if the steatosis, lipotoxicity, and lipoapoptosis of islets and myocardium occur in DIO as they do in rodents with congenital obesity (ZDF rats), and if anti-steatotic drugs such as troglitazone can improve islet and cardiac function; 2) To determine the mechanism of lipotoxicity in DIO, particularly the role of PPARalpha. This will include targeted over-expression of PPARalpha to the left ventricle of ZDF and DIO rats to determine if this prevents their steatosis, lipoapoptosis, and heart dysfunction. Delivery of the PPARalpha gene will be facilitated by a novel ultrasound technique developed by Dr. Paul Grayburn, a co- investigator of Project 3 of this application. We will also map the transcription start-site and promoter of the PPARalpha gene, as well as mechanisms of regulation of the gene in islet cells by leptin, taking advantage of the expertise of Dr. David Mangelsdorf, co-investigator, Project 1. Finally, PPARalpha knock-out mice will also be given a high fat diet with the expectation that they will be more vulnerable to lipotoxicity. These studies should provide new insights into the role of lipids in the development of tissue dysfunction associated with diabetes and obesity.
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